Photoelectric-controlled gasdischarge tube



April 20, 1943. c BENCH 2,316,772

PHOTO-ELECTRIC CQNTROLLED GAS DISCHARGE TUBE Filed March 2, 1940 1 /70 TOJENS/ T/VE 0477/00! [OW/1R0 CHARLES 05w Patented Apr. 20, 1943 PHOTOELECTRIC-OONTROLLED GAS- DISCHARGE TUBE Edward Charles Dench, South Orange, N. J.

Application March 2, 1940, Serial No. 321,936

3 Claims.

The present invention relates to dischar e devices. and more particularly to devices of this character controlled by photoelectric action.

An object of the invention is to provide a new and improved electrical controlling device of the discharge type that is controlled by the action of light or other radiant energy.

Another object is to provide a new and improved thermostatic or thermally-sensitive controlling device controlled through the photoelectric control of the flow of electrons, or ionization, within the tube, which flow or ionization, in turn, communicates heat to the thermally-responsive element or elements.

Still another object contemplates the use of a tube of the above-described character containing at least one electrode in addition to the thermostatic or thermally-responsive element or elements.

A further object is to provide a new and improved photoelectric relay, operating on the thermal principle, and that shall be simple and compact in construction and operation, and inexpensive to manufacture and operate.

Other and further objects will be explained hereinafter and will be particularly pointed out in the appended claims.

The invention will now be more fully explained in connection with the accompanying drawing, in which Fig. l is a diagrammatic view in section, of a tube embodying the invention, shown connected in a circuit illustrative of an intended use; and Fig. 2 is a similar view of a modification.

The tube envelope, container, or lamp II may contain gas, vapor, or other substance, or a combination of the same, providing a readily ioniza-ble medium at an optimum pressure below atmospheric. A suitable such gas is neon. According to a feature of the present invention, the tube I I is provided with at least one electrode in addition to a thermostatic or thermally-responsive element or elements. The electrodes are normally spaced in the container a predetermined distance from one another. The thermally-responsive element is shown as a photo-sensitive cathode 4 I 3 or H3, constituted of a bimetal strip coated with a photo-sensitive electron-emitting material. The photo-sensitive material may, for example, be caesium oxide on silver, which is capable of emitting electrons under the action of radiant energy. The cathode 5 I 3 is shown fixedly supporting at its free end a contact member I5, and the cathode 4|!- a contact'member 4 l 5. The tube II is shown provided also with an anode 4" or II, with or without a grid or other control electrode SIS, and

an electrode member H2 or M2 for supporting a cooperating contact member 4 or I4. The bimetal should be so designed that, upon a rise in its temperature, it shall flex to such position that the contact member I5 shall engage the contact member I4, or the contact member 4 l 5 shall engage the contact member 4, for the purpose of closing an electric circuit. The contact members I4 and l5or4I4 and4l5 are designedtocarry a comparatively large current. They need not be the simple ones shown; any combination of makeand-break contact members, operated directly or indirectly by thermal action, as hereinafter described, may be used.

The grid 5Ii may be constituted of solid material of any shape, although a mesh or perforated plate is preferred. The grid need not be disposed as shown; it may surround either the anode or the cathode. The anode 4 I I or 5", which may be of simple construction, is so situated in the tube II that it shall not interfere badly with rays of light impinging on the cathode H3 or 5I3.

The tube is shown so connected into circuit that a positive potential is impressed upon the anode 4I'l or 5H, suflicient to maintain a gaseous discharge in the tube, and the grid SIG (where employed) is so biased, through an impedance 2|, that the discharge is normally restrained from taking place. The cathode bimetallic strip 5I3 is shown connected in circuit with a resistor or potentiometer I9, supplied with energy from a .battery 20, and a ballast resistor or other impedance element I8 to the anode 5I'I, so as to impress a potential upon the anode 5" positive with respect to the cathode. The anode 5 is connected, through the resistor I8, to the positive side of the resistor I9, the cathode I3 is adjustably connected to the negative side of the resistor I9, and the grid 5l6 is connected, through the impedance 2|, to an intermediate point of the resistor I9. A suitable potential is thus impressed upon the grid 5H5, the value of which may be varied, by varying the connection of the grid SIS to the resistor I9, to cause the grid to control the flow and the energy of the electrons between the cathode I3 and the anode 5". In this manner, it is possible to permit the electrons to have sumcient energy to ionize the neon or other gas in the tube.

The cathode H3 or 5I3, carrying the contact member 5 or I5, may be connected to a binding post 3", and the member 2 or 5I2, carrying the contact member I4, to a binding post 9. The binding posts 3|! and II! may be connected to any desired external electric circuit or circuits,

the closing (or opening) oi which it is desired to control by the closing (or opening) of the contact members it and it. Such external electric circuit may, for example, contain any deried load (not shown) in series with a source of energy (not shown). The cathode electrode 8 or III maybe connected, through the binding post ill, to the energy source (not shown), and the electrode 4|! or III, through the binding post ill, to the load (not shown).

Assuming light rays or other radiant energy to tail upon the photo-sensitive cathode III or ill, electrons will be released thereirom, which will be attracted to the more positive anode Oil or III. This electron current will produce a voltage drop on the impedance 2! (in the circuit 01' Fig. 2), resulting in. a potential change oi the grid BIC. The pressure oi the ionizable medium in the envelope ii is oi such value that this voltagechange will eiiect a glow discharge between the anode electron Ill and the cathode electrode Ill. 11 the potentiometer or other grid-bias source has been suitably adjusted, bombardment oi positive gas ions upon the cathode will result in heating the bimetal strip Ill oi the cathode. The bimetal strip will thereupon flex to eiiect closing, through the medium oi the contact members It and ",0! the electric circuit connected to the binding posts ill and I". A thermostatically operated switch l4, I is thus provided, under the control of a photo-sensitive cathode Iii, that controls the gas discharge the action of which controls the heating of the thermostatic device.

Once thus closed, the circuit will remain closed, and the relay will operate, independently oi the the starting and stopping, or the control, oi the l grid, very much as takes place in a grid-glow tube. By appropriate means, however, the grid may be caused to stop the discharge. By energizing the tube from an altemating-current source of energy, ior example, the discharge will stop at each zero point 0! the cycle, thus permitting v the grid to regain control.

A tube of the described nature'has many applications where an electrical circuit needs to be closed in response to the action oi light or radiant energy. It is. very simple, cheap and efilcient, and it is capable oi carrying a large current. A tube oi this nature has application, for example, in control of illumination, where it is desired that lights be turned on when the level oi illumination in a room becomes too low. It is also adaptable for use in door openers, burglar alarms,

smoke alarms, etc.

The cathode 3 or 513 may be constituted of thermally-responsive material, not necessarily bimetallic. It may, for example, be constituted of a material that changes resistance with temperature. A device of this character may thus be employed to periorm useiul electrical operations by virtue oi such resistance changes.

Accordingto tube construction, electrode spacin gas pressure, etc., the grid may be designed to operate at either a positive or a negative bias, although a positive bias is preferred.

According to the modification. of Fig. 2, the cathode I is shown connected in circuitwith the battery 20 and a ballast resistor I, so as to impress a potential upon the anode ll'l positive with respect to the cathode. The anode-potential should be adjusted or regulated to a control value corresponding to the level 01' the illumination at which it is desired to operate the tube; that is, just below the level at which a discharge occurs in the tube when a low level of light or other radiant energy excites the photosensitive cathode.

Though the tube oi Fig. 2 is unprovided witha grid, the element I constitutes a cold cathode made of photosensitive material. The control oi the a may here, too, thereiore, be likened to the con 1 exerted by a grid, though the discharge is initiated by the action ,oi' light upon the cathode I, rather than through control secured by the action of light on a grid or similar control element.

This tube has applications similar to those of the tube in Fig. 1. Though simpler and cheaper, these advantages are counterbalanced by shorter life. The tube, however, is capable oi handling relatively large amounts at current.

The grid potential may be adjusted to vary the setting for the degree of illumination desired, thus producing break-down oi the gas in the tube at the desired point.

According to the present invention, therefore,

gaseous discharge may be eiiectedby the insertion, in the space of the tube, oi an element that is photosensitive, or coated with a photo-emissive material that, upon being subjected to light or other radiant energy, will emit electrons that will cause fields to be set up.

- Modifications will occur to persons skilled in the art and all such are considered to be within the spirit and scope of the invention, as defined by the appended claims. What is claimed is:

1. In combination, a gas-containing tube having two electrodes, namely, an anode and a photosensitive electron-emitting cathode, and having.

also a third electrode, cooperating contact members carried by the cathode and the third electrode, means for connecting a load circuit to the cathode and the third electrode, means for applying a voltage across the cathode and the anode, and means for regulating the voltage to a critical value corresponding to a level oi illumination on the cathode such that the cathode shall respond to emit sufllcient electrons for initiating a gaseous discharge between the anode and the cathode, thereby to produce positive ions for striking the cathode to heat it, and the cathode being deiormable in response to heat to eiiect actuation of the contact member carried thereby with respect to the other contact member, thereby to control the load circuit.

2. In combination, a gas-containing tube hav-- ing two electrodes, namely, an anode and a photosensitive electron-emitting cathode, and having also a third electrode, cooperating contact members carried by the cathode and the third electrode, means for connecting a load circuit to the cathode and the third electrode, means for applying a voltage across the cathode and the anode, and means for regulating the voltage to a critical value corresponding to a level of illumination on the cathode such that the cathode shall respond to emit suillcient electrons for initiating a gaseous discharge between the anode and the cathode, thereby to produce positive ions ior striking the cathode to heat it, and the cathode being bimetallic in order that it may respond to heat to effect actuation oi the contact member carried thereby with respect to the other contact member, thereby to control the load circuit.

3. In combination, a g as-containing tube hav-' ing two electrodes, namely, an anode and a photothird electrode, means for applying a voltage to the anode, means for applying a voltage to the control electrode, means for regulating the control-electrode voltage to a critical value corresponding to the level of illumination on the 10 cathode at which a gaseous discharge shall take place between the anode and the cathode, thereby to produce positive ions for striking the cathode to heat it, and the cathode being deformable in response to heat to effect actuation of the contact member carried thereby with respect to the other contact member, thereby to control the load circuit.

EDWARD CHARLES DENCH. 

